uniry shader 菲涅尔反射

Shader "Unlit/reflex"
{
	Properties
	{
		_MainTex ("Texture", 2D) = "white" {}
		_Cube("Cube", Cube) = "_Skybox"{}
		_Frac("菲涅尔近似参数", Range(0, 1)) = 0.5
	}
	SubShader
	{
		Tags { "RenderType"="Opaque" }
		LOD 100

		Pass
		{
			CGPROGRAM
			#pragma vertex vert
			#pragma fragment frag
			// make fog work
			#pragma multi_compile_fog
			
			#include "UnityCG.cginc"
#include "Lighting.cginc"
#include "AutoLight.cginc"
			struct appdata
			{
				float4 vertex : POSITION;
				float2 uv : TEXCOORD0;
				float3 normal : NORMAL;
			};

			struct v2f
			{
				float2 uv : TEXCOORD0;
				UNITY_FOG_COORDS(1)
				float4 vertex : SV_POSITION;
				float3 normal : NORMAL;
				float4 pos : TEXCOORD1;
			};

			sampler2D _MainTex;
			float4 _MainTex_ST;
			samplerCUBE _Cube;
			float _Frac;
			v2f vert (appdata v)
			{
				v2f o;
				o.vertex = UnityObjectToClipPos(v.vertex);
				o.pos = mul(UNITY_MATRIX_M, v.vertex);
				o.normal = mul(UNITY_MATRIX_M, v.normal);
				o.uv = TRANSFORM_TEX(v.uv, _MainTex);
				return o;
			}
			
			fixed4 frag (v2f i) : SV_Target
			{
				// sample the texture
				fixed4 col = tex2D(_MainTex, i.uv);
				float3 reflex = reflect(-UnityWorldSpaceViewDir(i.pos).xyz, i.normal);
				float4 ref = texCUBE(_Cube, reflex);
				float frac = _Frac + (1 - _Frac) * pow((1 - dot(normalize(UnityWorldSpaceViewDir(i.pos)),normalize( i.normal))), 5);
				// apply fog
				return lerp(col ,  ref ,   frac) ;
			}
			ENDCG
		}
	}
}